Rotary or drum-type cutting dies are commonly used for producing a corrugated board container or carton blank from corrugated board sheet material. Such rotary dies are typically comprised of a pair of cooperating cylinders or drums. One of the cylinders, a cutting cylinder, contains cutting blades or rules while the other, an anvil cylinder, provides a backing surface against which the cut is made.
Rotary cutting dies of the type described above are typically employed to trim the leading and trailing edges of the corrugated board blanks during a die cutting operation. As such, provisions for removing or stripping the severed trim scrap from the cutting die must be provided. Otherwise, if not actively removed from the vicinity of the cutting die, the scrap material tends to collect between the trim cutting blades and adjacent scrap strips which can result in serious damage to the die board and may ultimately render it inoperable.
Over the past decade, consumers have begun to demand corrugated board products that are completely or nearly completely free of the scrap resulting from die cutting operations. In certain applications, such as in the food packaging industry, it is not uncommon for the presence of minute quantities of scrap material dispersed amongst a stack or pallet of finished corrugated board packaging product to constitute grounds for rejection of the entire stack of product. Therefore, an additional consideration with regard to the stripping or ejection of corrugated board scrap, is the direction in which the successfully stripped or ejected scrap exits the cutting die assembly. As the usable product of the cutting process is typically expelled directly outward from the nip of the rotary cutting die assembly, it is desirable, in order to obtain complete separation of scrap and product, that the scrap be ejected from the rotating cylinders at a significantly different trajectory than the product.
In the past, resilient rubber pads or strips made of closed cell, high density foam or gum rubber have been placed immediately adjacent the edge trimming blades so as to forcibly eject the trimmed scrap material. However, previous resilient trim strippers have suffered from a number of shortcomings. In cases of lead trim strippers, the respective stripper pads are placed just forwardly of the lead trim blades. To be effective, these strippers must normally project outwardly past the trim blades. Because the strippers normally include generally flat sides and edges, the portion of the strippers that projects outwardly past the trim blades present an unforgiving, generally abrupt initial contact surface for incoming sheets of corrugated board. What typically happens here is that the lead edge of the corrugated board being fed into the die has a tendency to ram the side of the stripper projecting downwardly past the trim blade, causing the stripper to be urged forwardly away from the trim blade. When this ramming action repeats itself, as it can do in a die cutting operation, a number of problems can be anticipated. First, cut trim scrap often becomes jammed or lodged between the stripping member and the cutting blade. As scrap accumulates between the stripping member and the cutting blade, the resilient stripping member can be deformed so as to render it functionally ineffective and furthermore, can actually be pried loose from the cutting die to which it is mounted. In addition to damaging the stripping members, scrap accumulated in the vicinity of the cutting blade can also become wedged between the die board and the blade mounted therein. In such cases, the wedged scrap material may cause the blade to be loosened and begin to wobble within the die board, and in extreme cases, the wedged scrap material may actually crack the die board, rendering it inoperable.
In other cases, the accumulation of unwanted scrap material around the stripper may significantly alter the effective pliability or elastic characteristics of the resilient stripper. As such, the stripping member may actually deform the urethane coating on the adjacent anvil cylinder, thus rendering the cutting die assembly functionally ineffective.
Therefore, there remains a need for a practical, reliable, and cost effective resilient edge trim stripping member for use with corrugated board rotary cutting dies which prevents the accumulation of trim scrap material around the stripping member or members and which furthermore provides for directional control of the ejected or stripped scrap as it exits the rotary cutting die apparatus.